Rear rim wears out

P1010752- rim-broken The brake has obviously worn out the rim.
As soon as I went to check the rear hub I found the brake was rubbing on a severely bulged out and worn through section of the rear rim.
I had not picked this up as we had thought the dragging was the hub gears!
I re adjusted the rim brakes so they definitely do not touch the rim when not engaged.
In fact I have avoided using the rear rim brakes today since finding this problem:
P1010750-rim-2

This rim is a 20inch 36 spoke rim and I hope I can replace it in Meknes as I am concerned about riding too far in this condition. I feel it could blow out at any time. So far we are taking it slowly down hills using the drag brake only on the back and keeping below 30km/hour… usually 20.